The effect of different pre-treatment processes on the precipitation and hardening response of Al-Mg-Si-Cu was systematically studied by a combination of various characterization techniques. It was revealed that both of the pre-aging and pre-straining is unable to increase the peak aging hardness, but can accelerate the precipitation kinetics of the alloy as compared with single-stage aging. A novel multi-aging process consisted of high-temperature pre-aging (180°C for 2 h), followed by 5% pre-s